I won 2k last time walking into the hotel from a slot in the lobby @ Hilton in Fajardo =p
@Gadrel you will be fine, its like anywhere in the world if you use common sense. There is one VERY bad area of PR and its literally in the middle of el Morro and San Juan and its called La Perla. You would have to be a fool to drive into its only entrance guarded by military police and a lot of DEA. You can see it clearly though if you want a look from any of the towers at El Morro.
I can recommend a for sure spot you should visit when you arrive in PR for breakfast / lunch called Kasalta Bakery. You can get a good idea of how the early day food is from there. The typical breakfast is coffee & sweet bread pressed with real ham & cheese then covered in powdered sugar. You can also just get it plain or however you like. We have some weird shit going on with some of the food but its good. Our national sauce no lie is fancy sauce, its ketchup and mayo and served at every restaurant and sold bottled in the grocery stores. Another place that is really good for dinner and cheap is next to the national cock fighting arena in San Juan, its 5m from the airport. I forget the name but its so fucking good, you wont be dissapointed and you can see our lovely sport of cock fighting after dinner.
Besides the touristy things I would also recommend seeing the luminescent bay at night in Fajardo. You could do an early morning trip to Luquillo, which is known for its beaches and kiosk type shops that serve liqour, fried foods, and ceviches. It will be packed early with almost a hundred shops to choose from all with an incredible view. Everyone drinks Medalla beer or OJ + Vodka, people drink Finlandia Vodka like it came from Jesus's hands himself in Puerto Rico.
After breakfast I would go into the rainforest El Yunque and do it all, definetly drive or go near the top and see our tropical waterfalls. The view, waterfalls, and hikes are incredible with the ocean below you and you in a jungle. I like to take friends to the Hippy Waterfalls if you want specifics, you can hike up caves and waterfalls from there and spend the rest of the day doing crazy shit. A lot of locals go there and are friendly, youll be amazed the height and places they jump from.
After that I would at night goto the bioluminescent bay in Fajardo. All of these above are about 30-45m away from San Juan and on the Northeast side of the island. The bay has guys non small boats who will take you out at night (its illegal but no one cares). You can jump into the water or throw shells and watch it explode in colors. Its really beautiful to see no matter how many times ive seen it.
If you want to also see a gem we dont have here in the US where I am there is also Sizzler in PR and Ponderosa.